TO THE EDITOR
Cholangitis, fibrosis, and eventually cirrhosis are the results of chronic inflammation and fibrotic destruction of interlobular bile ducts in primary biliary cholangitis (PBC), a rare autoimmune and cholestatic liver disease[1]. Ursodeoxycholic acid (UDCA) has been the first-line treatment for PBC for the past 20 years, helping to delay the progression of the disease and increase the amount of time before liver transplantation is required[2]. Between six months and two years, UDCA is effective; but, in the absence of adequate early care, the disease is likely to progress during this time[3]. As a result, it's important to promptly identify PBC patients who have not responded completely to UDCA, quickly start drug therapy, delay histological development, and improve prognosis. To detect differentially expressed genes (DEGs) and reveal important biological pathways linked to PBC pathogenesis, microarray bioinformatics techniques were applied[4]. Consequently, Zang et al[5] study aimed to determine the important biomarkers in the development of PBC, elucidate the factors influencing UDCA's efficiency, and increased early treatment methods.
RESEARCH PLAN AND STATISTICAL VALIDATION
The experimental scheme of Zang et al[5] study included 197 PBC patients and 71 HCs who were collected between January 2018 and April 2023 from Qingdao University in China. The presence of anti-mitochondrial antibodies, biochemical analysis of cholestasis, and histological analysis of destructive cholangitis and interlobular bile duct damage in liver biopsy were the basis for the diagnosis of PBC. Fatty liver, autoimmune hepatitis, hepatitis B virus infection, drug-induced liver injury, hepatocellular carcinoma, myelodysplastic syndrome, and primary myelofibrosis were among the criteria that were excluded. A total of 71 PBC patients and 71 HCs had their liver tissue collected. This study endpoint was one year after the start of UDCA treatment, and the follow-up started at the time of PBC diagnosis. Using the Paris criteria, the 71 PBC patients were divided into UDCA responders and UDCA non-responders[6,7]. UDCA was administered as a regular treatment to all patients (13-15 mg/kg/day). Gender, age, clinical symptoms (such as fatigue or pruritus), previous medical history, and laboratory tests (such as platelets, albumin, total bilirubin, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, gamma-glutamyl transpeptidase, and total bile acid) were all measured clinically for each study participant. The study included immunohistochemistry, DEGs identification, biochemical response to UDCA, and histological examination. Zang et al[5] study used the "t" test or the Mann-Whitney U test in the statistical analysis to make sure their findings were accurate. Data correlation was evaluated using Pearson's correlation coefficient. The predictive values were compared using receiver operating characteristic curves. The statistical analyses were conducted using SPSS version 25 (IBM, Armonk, NY, United States).
A NEW BIOMARKER FOR PBC DIAGNOSIS
The study detected thirteen important genes in PBC patients by bioinformatics analysis and these genes included MYOF, NEDD9, CELF2, SSH2, SEMA4D, tumor necrosis factor alpha-induced protein 3 (TNFAIP3), TAGAP, BTLA, ARRDC2, FAHD1, PNP, SUMO1, and UT. TNFAIP3 was subsequently chosen for more investigations. By stopping nuclear factor kappaB (NF-κB) activity, the ubiquitin-editing enzyme TNFAIP3/A20 controls inflammation. TNFAIP3/A20 has a C-terminal domain that provides E3 ubiquitin ligase activity and an N-terminal domain that is necessary for its deubiquitylating activity[8]. When NF-κB is activated, TNFAIP3 expression is quickly increased and it acts as a negative feedback regulator to prevent more NF-κB signaling[9]. Tumor necrosis factor (TNF)-mediated programmed cell death and NF-κB activity are inhibited by TNFAIP3/A20. In every tissue, TNF significantly increases the expression of TNFAIP3/A20 messenger RNA. TNFAIP3/A20-binds to: (1) Inhibitor of NF-κB activation; (2) Inhibitor of NF-κB kinase gamma (IKKγ); and (3) TNF receptor–associated factor-2. There is a correlation between the synthesis of survival proteins (Bcl-2 and Bcl-x) by NF-κB-dependent pathways and stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK)[10]. Therefore, all NF-κB- and SAPK/JNK-dependent survival proteins are synthesized by TNF. TNF induced the degradation of inhibitor of κB alpha (IκBα) and NF-κB binding to DNA, which was followed by NF-κB binding being down-regulated and IκBα protein reaccumulating. TNF caused a rise in IκBα mRNA levels, which were transcriptionally increased by NF-κB[11]. The action of IKK (a multimeric complex that includes IKKα, IKKβ, and IKKγ) quickly phosphorylated the freshly generated IκBα protein. Therefore, without TNFAIP3/A20, IκBα mRNA and IκBα protein synthesis alone cannot stop NF-κB signals. Because IKKγ is necessary for TNF-induced NF-κB activation, TNFAIP3/A20 prevents TNF from activating the NF-κB pathway upstream of IKKγ[12]. In summary, TNF-induced NF-κB signals are inhibited by TNFAIP3/A20, indicating that these signals may be differentially controlled in vivo. Therefore, controlling inflammatory reactions and their harmful effects in different organs depends on the quick expression of TNFAIP3/A20. TNF significantly increased the expression of TNFAIP3/A20 mRNA in all tissues. Therefore, TNFAIP3/A20 is therefore essential for reducing inflammation by stopping TNF-induced NF-κB responses in vivo.
IMPLICATIONS FOR CLINICAL PRACTICE
The outcomes from Zang et al[5] study have important consequences for PBC management. The results revealed that, the prevalence of fatigue, higher levels of gamma-glutamyl transpeptidase, alkaline phosphatase, and total bilirubin, as well as higher levels of anti-gp210 antibody (an autoantibody linked to PBC that targets the gp210 protein) and TNFAIP3 expression, were all significantly higher in UDCA non-responders than in UDCA responders. On the other hand, Anticentromere antibody was less common in UDCA non-responders. The function of TNFAIP3 was examined in PBC patients by classified TNFAIP3 expression levels in PBC patients into two groups; TNFAIP3-high (n = 28) expression and TNFAIP3-low (n = 43) expression. Pathological characteristics, immunological markers, metabolic information, clinical symptoms, and demographics were among the clinical parameters measured between the two groups in the study. The results showed that the TNFAIP3-high group showed a higher incidence of splenomegaly, a significant higher level of alkaline phosphatase, and a younger age at onset (46 years in the TNFAIP3-high group) compared to 53 years (older age at onset) in the TNFAIP3-low group. Total bilirubin, alkaline phosphatase, and splenomegaly all revealed positive correlations with TNFAIP3, while age and albumin showed inverse correlations. Liver fibrosis and TNFAIP3 expression had a weakly negative connection with TNFAIP3 that was not statistically significant.
TNFAIP3 AS A SMALL MOLECULE MODULATOR, A MONOCLONAL ANTIBODY, AND IN GENE THERAPY
Beside the application of TNFAIP3 as a useful biomarker for PBC treatment, it is used also as a small molecule modulator, a monoclonal antibody, and in gene therapy. TNFAIP3 is used as a small molecule modulator by increasing the expression of cyclin-dependent kinase 5 (CDK5) in brain tissues and multiple myeloma[13]. TNFAIP3 is used also as a monoclonal antibody, because TNFAIP3 has two areas (rs610604 and rs6920220) that are significantly linked to an improvement in quality of life at both the 3- and 6-month phases of arthritis patients. Consequently, TNFAIP3 plays an important role in the improvement of arthritis patients' reaction to a specific drug. Furthermore, tumor-derived exosomes can penetrate tumor cells and target TNFAIP3, decreasing the tumors' sensitivity to anticarcinogenic drugs, which aids in the development of new therapeutic antitumor treatments[14].
In additional application, TNFAIP3 is essential for gene therapy through its effects on the repressor downstream regulatory element antagonist modulator and its nuclear and cytosolic function to regulate inflammation, particularly in cystic fibrosis, asthma, and chronic obstructive pulmonary disease[15]. Additionally, through the NF-κB signaling pathway, TNFAIP3 controls the production of ubiquitin C terminal hydrolase L1 in lupus nephritis, and consequently TNFAIP3 protein is a suitable treatment for lupus nephritis[16]. Furthermore, TNFAIP3 is essential for the negative control of innate immune responses during chronic viral infection since its expression is correlated with the activity of myeloid dendritic cells during hepatitis C virus infection and interferon-α therapy[17].
THE FUTURE OF PBC BIOMARKERS
The forthcoming development of predictive diagnostic techniques will support PBC management trends. Future research must investigate the role and molecular processes of TNFAIP3 in the beginning and progression of PBC. It is advised to conduct a detailed investigation utilizing both in-vitro and in-vivo experiments to determine how TNFAIP3 expression can predict UDCA response and, in turn, control and treatment of PBC progression. Zang et al[5] study based on biochemical markers measured one or two years following treatment. However, the majority of previous research[18] shows that most PBC patients undergo histological progression and development within the first one to two years if early prediction is not made. Therefore, in order to prevent PBC complications and progressions, future research must focus on early treatment response during the first year of PBC discovery.
STRENGTHS AND LIMITATIONS
Zang et al[5] study used TNFAIP3 as a PBC diagnostic agent and this finding is its main strength. The liver tissues of PBC patients showed a significant expression of TNFAIP3, indicating that TNFAIP3 may control the pathophysiology of PBC. On the contrary, demographic characteristics including age and sex[19], serum biochemical indicators[7], autoantibodies[20], clinical symptoms like fatigue and pruritus[21], and histological results[22] have all been found to be predictive of response to UDCA in previous researches.
Zang et al[5] study limitations include: (1) The study only used microarray data for transcriptional profiling; it did not integrate microarray data with genomic, proteomic, or metabolomic data. The microarray data were taken from publicly available datasets and were not produced by the authors; (2) The study's statistical power may have been limited by the small sample size used for analysis and verification, making it challenging to identify small factors or correlations. Because small sample size frequently result in overestimation of effects or an increased risk of statistical errors, this could have an impact on the study's conclusions' robustness and generalizability; and (3) There was no confirmation of the TNFAIP3 levels in the blood samples of PBC patients.
CONCLUSION
NFAIP3 was chosen as one of the 13 genes linked to PBC progression, and PBC patients' expression of TNFAIP3 was significantly higher than that of HCs. TNFAIP3 and fatigue were both independent risk factors for PBC patients' response to UDCA. Additionally, there was a correlation between TNFAIP3 expression and splenomegaly, alkaline phosphatase, albumin, total bilirubin, and age. Future studies must focus on early drug response in the first year of PBC discovery, where histological development and progression occur in PBC patients within the first one to two years. By integrating genomic, proteomic, and metabolomic data besides increasing the sample size, TNFAIP3 could be utilized as a suitable biomarker or therapeutic target for PBC in the future, enabling precise disease monitoring and treatment modifications.
Provenance and peer review: Unsolicited article; Externally peer reviewed.
Peer-review model: Single blind
Specialty type: Gastroenterology and hepatology
Country of origin: Egypt
Peer-review report’s classification
Scientific Quality: Grade B
Novelty: Grade C
Creativity or Innovation: Grade C
Scientific Significance: Grade B
P-Reviewer: Jiang X, PhD, China S-Editor: Liu JH L-Editor: A P-Editor: Zhang YL
